KIRUNA, Sweden -- The unusually balmy winter that has kept bears awake and spoiled ski holidays across Europe is taking a major toll on Sweden's indigenous Sami reindeer herders, and it may take them years to recover.

Heavy wet snows and big temperature swings have iced over swaths of Lapland, making it hard for Sami reindeer herds to dig down to the white reindeer moss that is their natural food.

"In some areas the grazing is totally locked," said Niklas Labba, a Sami reindeer herder and academic.

With the Arctic expected to suffer the most extreme effects of global warming, atypically mild winters may become the norm -- and that, herders say, could endanger traditional Sami life.

"We are forced to feed the reindeer and this will affect many herders economically. We have lost many hundred thousand crowns so far this winter," said Ola Rokka, a herder from the Swedish province of Norbotten.

There have been warmer winters -- 1929 was the mildest December ever for Kiruna -- but climate experts say unusually warm spells have become more frequent and more widespread.

Sweden's meteorological office said the average temperature in Kiruna was minus 7 degrees Celsius (19.4 degrees Fahrenheit) in December, versus a normal minus 14 degrees, with snowfall well above average.

Reindeer can smell moss through as much as a metre of snow, but can easily starve if they cannot reach it.

Herders who can track down all their animals in the forests and mountain areas where they roam can use factory food to keep them alive, although this brings its own problems.

"It is very expensive," said Nils Torbjorn Nutti. He said it costs 5 Swedish crowns ($0.710) a day to factory feed each reindeer.

Calculating the financial impact on an individual herder is difficult since asking a Sami how many reindeer he has is a social blunder akin to inquiring the size of his salary.

"That's a question you never ask a Sami," Nutti said.

He and his fellow herders agree that a minimum of 600 animals is necessary to subsist on herding alone. There are an estimated 240,000 reindeer in Sweden.

Nutti keeps bull reindeer in forest pens near the town of Jukkasjarvi for tourists, but he has also trucked calves in from the mountains since they are too young to shift the heavy snow.

"When you start to feed them now so early ... you must do it until the snow has melted, and that's not before the end of April or the middle of April," Nutti said. Delicate reindeer digestion doesn't adjust well to change.

"If you let them go out to the forest, they may be starving and dying."

TREELINE RISING

The Sami parliament plans to seek government money for the hardest-hit herders. Spokeswoman Marie Enoksson said authorities will assess how much to request later this month, once the 51 Sami regions, or "villages", submit applications.

Still, the grazing problem is likely to erode the herders' already lean profits and may have far-reaching effects on those who depend on selling calves, since weakened females often have trouble giving birth, Labba said.

Mild winters pose other problems for reindeer.

Lakes are freezing later, making it hard to move animals to easier grazing, and vegetation is filling once-open areas.

Christer Jonasson of the Abisko Scientific Research Station in northernmost Sweden said the tree line -- the altitude beyond which it is too cold for trees to grow on a mountain -- has risen by 20 metres (22 yards) in the past 40 years.

"If you should extrapolate this there will be dramatic changes (in the tree line) in the next few decades," said Jonasson, who with his Abisko colleagues runs joint projects with the Sami to create a richer picture of the Arctic.

"Mountain reindeer are dependent on these tree-free areas."

Abisko's work has shown temperatures and snowfall have been on a rising trend since the late 1980s. Some say a prolonged string of such warm winters could make a herding life impossible to afford.

This would threaten more than just the animals, as Sweden only gives special rights -- to use land, water, and to hunt -- to the 10 percent of the 20,000 Swedish Sami who herd reindeer.

"If the reindeer were to die away, then the Sami would have no rights anymore," Labba said.

Nutti said for him, losing reindeer herding would mean the end of Sami culture, even if herders found other work.

"The highest (goal) for us is to be a reindeer herder and a good reindeer herder. That is the best that we know," he said.